Soft contact lenses have been available since the 1980s. Currently there are two types of soft contact lenses. “Conventional” lenses are made from hydrophilic polymers such as poly(2-hydroxyethyl methacrylate) (PHEMA) and copolymers of N-vinyl pyrrolidone and methyl methacrylate. These contact lenses have relatively low permeability to oxygen (typically below 8-30 barrers), but high water content (typically in excess of 35%). Examples of a conventional soft contact lens include Acuvue® and Acuvue2® brand contact lenses, both of which are considered as among the most comfortable soft contact lenses commercially available. However, many lens wearers cannot comfortably wear conventional lenses for a full day (up to nine hours or more).
Contact lens wearers commonly report symptoms of dryness and discomfort while wearing contact lenses. These symptoms can be exacerbated in environments prone to low relative humidity, such as pressurized airline cabins, home or office environments that use forced-air heating or air-conditioning systems, as well as locales and environments subject to low ambient humidity. The relative humidity in commercial airlines commonly ranges from as low as 5% to under 40%, with mean values averaging between 14-19%.
Silicone hydrogel contact lenses contain silicone in the lens polymer. Silicone increases the lens's oxygen permeability, which contributes to the lenses ability to be worn for longer periods of continuous wear. However, commercially available silicone hydrogel contact lenses are perceived by many lens wearers to be less comfortable than conventional contact lenses. Accordingly, there remains a need in the industry for a contact lens which can be worn comfortably for a full day of wear, even in low humidity environments.